Search PubMed⌕ Search

Biomedical subjects

M H Friedman

Publications and source records attributed to M H Friedman.

At least 91 records · Page 5Linked to original sources
PubMed1981

Correlation between intimal thickness and fluid shear in human arteries.

A realistic pulsatile flow was passed through a cast of the aortic bifurcation of a 63-year-old male with mild atherosclerosis, and a laser Doppler anemometer was used to measure fluid velocities in the cast at 15 selected sites near the lateral and medial walls. Intimal, medial and adventitial thickness were measured, and sudanophilia was scored, at corresponding sites in the vessel from which the cast had been made. A negative correlation was found between intimal thickness (IT) and wall shear rate (i.e., the velocity gradient at the blood-artery interface). The strongest negative correlation (P less than 0.005) was between IT and "pulse shear rate" (PSR), defined by analogy with pulse pressure. Sudanophilia also correlated negatively with PSR (P less than 0.01). These results suggest that large excursions of interfacial shear, at levels too low to cause damage, may inhibit intimal thickening.

Arteries↗
PubMed1981

Transport across homoporous and heteroporous membranes in nonideal, nondilute solutions. I. Inequality of reflection coefficients for volume flow and solute flow.

The Kirkwood formulation of the Stefan-Maxwell equations is used to develop the transport equations for a membrane bounded by nonideal, nondilute solutions. The reflection coefficients for volume flow and solute flow are not equal but are related by a simple expression that depends on the concentration of the bounding solutions. The ratio of the two coefficients is independent of heteroporous membrane structure and the thickness of adjacent boundary layers. Experimental measurements of these reflection coefficients for sucrose transport across Cuprophan verify this relationship; this indicates that the Onsager reciprocal relation, which is assumed by the theory, holds for nonideal, nondilute solutions. The two reflection coefficients may be made operationally identical by a simple redefination of the osmotic driving force.

Biological Transport↗
PubMed1981

Transport across homoporous and heteroporous membranes in nonideal, nondilute solutions. II. Inequality of phenomenological and tracer solute permeabilities.

The phenomenological solute permeability (omega p) of a membrane measures the flux of solute across it when the concentrations of the solutions on the two sides of the membrane differ. The relationship between omega p and the the conventionally measured tracer permeability (omega T) is examined for homoporous and heteroporous (parallel path) membranes in nonideal, nondilute solutions and in the presence of boundary layers. In general, omega p and omega T are not equal; therefore, predictions of transmembrane solute flux based on omega T are always subject to error. For a homoporous membrane, the two permeabilities become equal as the solutions become ideal and dilute. For heteroporous membranes, omega p is always greater than omega T. An upper bound on omega p- omega T is derived to provide an estimate of the maximum error in predicted solute flux. This bound is also used to show that the difference between omega P and omega T demonstrated earlier for the sucrose-Cuprophan system can be explained if the membrane is heteroporous. The expressions for omega P developed here support the use of a modified osmotic driving force to describe membrane transport in nonideal, nondilute solutions.

Biological Transport↗
PubMed1981

Correlation of human arterial morphology with hemodynamic measurements in arterial casts.

A realistic pulsatile flow was passed through a cast of the aortic bifurcation of a 63-yr-old male with mild atherosclerosis, and a laser Doppler anemometer was used to measure fluid velocities in the cast at 15 selected sites near the lateral and medial walls. Intimal, medial and adventitial thicknesses were measured and sudanophilia was scored at corresponding sites in the vessel from which the cast had been made. A negative correlation was found between intimal thickness (IT) and wall shear rate. The strongest negative correlation (p less than 0.005) was between IT and "pulse shear rate" (PSR), defined by analogy with pulse pressure. Sudanophilia also correlated negatively with PSR (p less than 0.01). Medial thickness correlated positively with shear rate, and most strongly with the mean (i.e., time-average) rate (p less than 0.005). From an analysis of the fluid mechanical data, it appears possible to separate the effects of bifurcation geometry and the shape of the arterial cross section on interfacial shear.

Aorta↗
PubMed1980

A biochemical and ultrastructural study of skeletal muscle from rats fed a magnesium-deficient diet.

In order to study changes in skeletal muscle during a magnesium deficiency, serum and muscle tissues were collected from male Sprague-Dawley rats fed either a control or magnesium-deficient diet. The rats were killed on days 7, 10, 14, 17, 19, 21 and 26 of the experiment. Ion concentrations in serum and muscle were determined by atomic absorption spectrophotometry, taurine concentrations of serum and muscle were determined by the Pentz method, and ultrastructural changes in skeletal muscle were detected with the use of the transmission electron microscope. The results indicated an increase in serum taurine which preceded an increase in muscle taurine concentration in rats fed a magnesium-deficient diet. The electron micrographs showed a swelling of mitochondria on day 14 of the deficiency and a total disorganization of the sarcoplasmic reticulum by day 26. In conclusion, in skeletal muscle from rats fed a magnesium-deficient diet, major ultrastructural changes apparently occur after the serum magnesium concentration is reduced and about the same time as muscle taurine concentration becomes elevated. The changes may be initiated by alterations in membrane permeability which may be influenced by taurine, since taurine has been shown to influence ion movement across membranes or membrane stability.

Animals↗
PubMed1979

Hypophysectomy-induced inhibition of augmented acetylcholine responses of the rat bowel following adrenalectomy and/or whole body irradiation.

Functional changes in the intestinal responsiveness to a fixed dose of acetylcholine were studied in muscle strips removed from young adult male rats previously exposed to whole body gamma radiation. In the irradiated rat the responsiveness to a fixed dose of acetylcholine was found to be augmented in the small intestine but not in the colon. Similar motor patterns for the small intestine were found when muscle strips from adrenalectomized rats were studied. Preradiation adrenalectomy further exaggerated the post-radiation sensitivity of the rat small intestine to acetylcholine. Hypophysectomy prior to either adrenalectomy and/or whole body radiation was associated with an absence of augmented small intestinal motor activity following administration of acetylcholine. The response of the large bowel to acetylcholine, however, was not modified by adrenalectomy and/or hypophysectomy. These observations suggest an endocrine component to the acute 3--5 day intestinal radiation syndrome.

Acetylcholine↗
PubMed1978

Mathematical modeling of transport in structured tissues: corneal epithelium.

A computer model has been constructed to describe multi-ionic transport across an epithelium consisting of a transcellular pathway in parallel with a shunt. The model is parameterized to simulate rabbit corneal epithelium. Calculations show that when this tissue is stimulated by epinephrine at open circuit, there is a flux of electrolyte across it into the tears. The magnitude of the flux is sensitive to paracellular resistance, which also affects the potentials across the mucosal cell border and entire epithelium. The electrolyte extrusion rate of the tissue is found to be near zero in the absence of stimulation. More generally, it is shown that for epithelia whose structure is at least as complex as that used here, the active transport rate of ions exceeds their net flux at short circuit; tracer fluxes in one direction at two polarizations cannot be used to identify active transport or significant tracer interactions; and tracer measurements yield ionic permeabilities only at short circuit and only if the ion is not actively transported.

Animals↗
PubMed1978

An ultrastructural study of avian synovium infected with an arthrotropic Mycoplasma, Mycoplasma synoviae.

Live Mycoplasma synoviae cells in agar base medium were inoculated intravenously into 10 2-week-old chickens. Joint tissues were collected over a 3-week period for light and transmission electron microscopy. In infected chickens, membrane-bound vacuoles of intact M. synoviae cells were seen in the cytoplasms of adipose cells. Cytoplasmic lipid-containing inclusions had accumulated in enlarged fibroblasts in tendon sheaths and loose connective tissue. Synovial cells had proliferated and contained increased amounts of granular endoplasmic reticulum and lipid inclusions. No abnormalities were seen in control chickens. Infected chickens were positive and control chickens were negative for rheumatoid factor activity by two serological tests: tanned cell hemagglutination and latex agglutination tests.

Animals↗
PubMed1977

Venous aneurysms.

Primary venous aneurysms are rare lesions, but they can sometimes lead to serious complications. A report of a venous aneurysm in an unusual location is presented, with a review of the literature.

Adolescent↗